Method and device for triggering at least one firing element for a restraining means in a motor vehicle

ABSTRACT

The invention relates to a method and a device for triggering at least on firing element ( 6, 7, 8 ) for restraining means in a motor vehicle. In said method and device a firing command ( 3 ) is transmitted from a control unit ( 2 ) to a firing device ( 5 ) for the firing elements. The firing command ( 3 ) is subsequently repeatedly n-fold, whereby n is at least equal to 1. The n+1 transmitted firing commands are evaluated in the firing device and once the last of the n+1 firing commands has been transmitted, the firing elements are triggered.

[0001] The invention relates to a method and a device for firing atleast one firing element for a restraining means in a motor vehicle.

[0002] Arrangements for firing a restraining means in a motor vehicleusually have a sensor for detecting an accident, a control device whichis connected downstream of the sensor, the firing device which isarranged spatially separated from the control device and is connected toit via a line, and at least one firing element (for example a firingcap) for the restraining means, said firing element being electricallyconnected to the firing device.

[0003] If, for example, a plurality of firing caps are to be firedsimultaneously in such a context using a firing command, but not all thefiring caps detect the first firing command and/or fire, thetransmission link which is usually embodied as a firing bus between thecontrol device and the firing device may, under certain circumstances,be disrupted to such an extent that no further firing commands can betransmitted. This is the case, for example, if a short circuit or aninterruption at the bus occurs as a result of individual undesireddetonations. It is then no longer possible to fire the remaining firingcaps since no further firing command can be transmitted.

[0004] The object of the invention is to specify a method and anarrangement for firing at least one firing element for a restrainingmeans in a motor vehicle which provide a higher degree of immunity tofaults.

[0005] The invention is achieved by means of a method according topatent claim 1 and by means of a device according to patent claim 4.

[0006] Refinements and developments of the idea of the invention are thesubject matter of the subclaims. The invention provides for the firingcommands first to be transmitted repeatedly (for example 3 times), forfiring to be delayed during this time, and for firing of the firingelements, for example by means of the first firing command, to bepermitted only after the multiple transmission.

[0007] In particular, this is achieved by means of a method having thesteps described below. Firstly, a firing command is transmitted, andthen the firing command is transmitted n times, from a control device toa firing device for the firing element/elements, n being at least equalto 1. Then, the n+1 transmitted firing commands are evaluated in thefiring device and the firing element or elements is/are fired by thefiring device after the transmission of the last n+1, for example by thefirst firing command.

[0008] The firing actuation of the firing elements is preferablyrepeated here at least once or, for the sake of simplicity, coupled tothe number of transmitter firing commands in order to fire firingelements which have erroneously not yet been fired. Moreover, inaddition to simultaneous firing of the plurality of firing elements, itis also possible to provide for the chronologically offset firing of thefiring elements so that the firing elements are fired in succession.

[0009] A device according to the invention contains a control device forgenerating n+1 identical firing commands, a firing device for firing theat least one firing element by connecting the firing signal to thefiring element, and a transmission device for the transmission of thefiring commands by the control device to the firing device. Here, thefiring element is not fired by the firing device until after thetransmission of the last of the n+1 firing commands, for example by thefirst firing command.

[0010] In order to ensure that the firing of the firing element orelements takes place after the last of the n+1 firing commands has beentransmitted, with the control device a delay device is provided fordelaying the firing signal, the delay device being fired by the firstfiring command and having a delay which is longer than the time which isnecessary for the transmission of all the firing commands. The use of adelay device makes it possible for the firing element or elements to beoperated in such a way that firing cannot disrupt the transmission ofthe firing commands and/or said firing elements are not made to fireuntil the firing signal has been repeated several times.

[0011] In order to be able to increase the immunity to faults further,the firing commands in the control device can be encoded and transmittedto the firing device in encoded form. The firing device contains afiring command decoder in order to decode the firing commands and togenerate the firing signals for the firing elements from them.

[0012] Finally, it is possible to provide for a plurality of firingelements to be fired in succession by the firing device in order tobring about more uniform loading of the power supply for the firingelements.

[0013] The invention is explained in more detail below with reference tothe exemplary embodiments illustrated in the figures of the drawing, inwhich:

[0014]FIG. 1 shows a first exemplary embodiment of a device according tothe invention for simultaneously firing a plurality of firing elements,

[0015]FIG. 2 shows a further exemplary embodiment of a device accordingto the invention for firing a plurality of firing elements withstaggered timing, and

[0016]FIG. 3 shows a third exemplary embodiment of a device according tothe invention for firing a plurality of firing elements with staggeredtiming.

[0017] In the exemplary embodiment shown in FIG. 1, an impact sensor 1is provided, downstream of which impact sensor 1 a control device 2 forevaluating the signals supplied by the impact sensor 1 is connected. Inthe event of an impact, this is signalled to the control device 2 bymeans of appropriate signals of the sensor 1, in response to which saidcontrol device 2 transmits, for example, three firing commands 3 to afiring device 5 via a line 4. These firing commands 3 are identified bythe firing device 5. After a specific number of identical firingcommands 3 (for example a number of firing commands 3 transmitted intotal corresponding to the firing command in the exemplary embodiment),three firing caps 6, 7, 8 which are provided as firing elements thenbeing fired by the firing device 5. For this purpose, a firing signal(current, voltage) of sufficient strength is applied to the firing caps6, 7, 8 when the first delayed firing command occurs. The firing capsare supplied by means of a supply voltage source (not illustrated inmore detail) with a reference potential 10 and a supply potential 11. Inorder to prevent voltage dips in the supply voltage source when thefiring caps 6, 7, 8 are fired, a buffer capacitor 9 is also connectedbetween the reference potential 10 and the supply potential 11.

[0018] The firing device 5 contains a decoding device 12 which decodesthe firing commands 3 which are encoded by the control device 2 by meansof a coding device 13. A delay device 14, which delays the firingcommands 3 until all the firing commands 3 have been transmitted fromthe control device 2 to the firing device 5, is connected downstream ofthe decoding device 12.

[0019] This means that the firing command which is first transmittedappears at the output of the delay device 14 when the last of the firingcommands 3 has already been transmitted from the control device 2 to thefiring device 5.

[0020] The output of the delay device 14 controls the base terminals ofthree transistors 15, 16, 17 whose emitter-collector paths are connectedin series with the firing caps 6, 7, 8 between the reference potential10 and the supply potential 11. When the corresponding number of firingcommands occurs, the first firing signal which is delayed by the delaydevice 14 is therefore made available by the decoding device. Thedelayed signal then connects through the transistors 15, 16 and 17, as aresult of which the latter make available a firing signal for the firingcaps 6, 7, 8. In this case, the firing caps 6, 7, 8 are connected to thesupply voltage source, as a result of which the latter fire essentiallysimultaneously.

[0021] However, it is also alternatively possible to provide for thedelay device to be switched upstream of the decoding device and for thelatter to control the output of the decoding device 12 directly. Thismeans that the firing commands 3 arrive at the decoding device 12 withdelay and then the transistors 15, 16, 17 connect the firing caps 6, 7,8 to the high voltage source.

[0022] Furthermore, the decoding device and the delay device may beconstructed in such a way that the transistors 15, 16 and 17 areconnected through corresponding to each of the firing commands 3, thefiring caps 6, 7, 8 not being able to be connected through by means of afiring command alone (power of an individual firing signal is too low)and being fired only after a plurality of firing signals (correspondingto the firing commands 3 which follow one another at short timeintervals.

[0023] The exemplary embodiment shown in FIG. 2 is modified incomparison with the exemplary embodiment according to FIG. 1 in that afiring device 18 is used instead of the firing device 5. The firingdevice 18 comprises three decoding devices 19 a, 19 b, 19 c whichreceive the firing commands 3 from the control device 2 via the line 4.The decoding devices 19 a, 19 b, 19 c each have delay devices 20, 21, 22connected downstream of them, the inputs of said delay devices 20, 21,22 each being connected to the output of one of the decoding devices 19a, 19 b, 19 c. The delay devices 20, 21, 22 have different delays fromone another, each of the delays being longer than the time which isrequired for the transmission of the three firing commands 3 from thecontrol device 2 to the firing device 18. The delay devices 20, 21, 22are each followed by a transistor 23, 24, 25 for connecting the firingcaps 6, 7, 8 to the supply voltage. Owing to the delays of the delaydevices 20, 21, 22 which are different from one another but longer incomparison with the transmission time period, sequential firing of thefiring caps 6, 7, 8 thus occurs which has, inter alia, the advantagethat the supply voltage source (and the capacitor 9) are not as heavilyloaded as when there is simultaneous firing of the firing caps 6, 7, 8.

[0024] The exemplary embodiment according to FIG. 3 is based on theexemplary embodiment shown in FIG. 2 in that a firing device 26 is usedin FIG. 3 instead of the firing device 5 in FIG. 1. The firing device 26contains a decoding device 27 for receiving the firing commands 3 fromthe control device 2 via the line 4. The decoding device is followed bya delay device 28 which has a delay device 29 connected downstream ofit, followed by a delay device 30. A transistor 31, 32, 33 which isprovided for connecting the firing caps 6, 7, 8 to the supply voltage isconnected to the output of in each case one of the delay devices 28, 29,30.

[0025] Here, the delay device 28 which directly follows the decodingdevice 27 has a delay which is longer than the time required for thetransmission of the firing commands 3. The delays of the delay devices29 and 30 are, in contrast, freely selectable.

[0026] The embodiments shown are therefore suitable for carrying out amethod according to the invention in which a firing command aretransmitted repeatedly by the control device to the firing device forthe firing element (firing caps). In the firing device, the transmitterfiring commands are evaluated and, after the firing commands have beentransmitted, the firing caps are fired with a delay. The delay can beimplemented here either by means of a sufficiently dimensioned delay orelse by counting the firing commands.

1. A method for firing at least one firing element (6, 7, 8) for arestraining means in a motor vehicle having the steps: a firing command(3) is transmitted from a control device (2) to a firing device (5) forthe firing element or elements, the transmission of the firing command(3) from the control device to the firing device is repeated n times, nbeing at least equal to one, the n +1 transmitted firing command (3) areevaluated in the firing device (5), and the firing elements are fired bythe firing device after the last of the n+1 firing commands has beentransmitted.
 2. The method as claimed in claim 1, in which the firing ofthe firing element or elements (6, 7, 8) is repeated at least once. 3.The method as claimed in claim 1 or 2, in which the firing element orelements (6, 7, 8) is/are fired successively.
 4. A device for firing atleast one firing element (6, 7, 8) for a restraining means in a motorvehicle having a control device (2) for generating n+1 identical firingcommands (3), a firing device (5) for firing the firing element orelements (6, 7, 8) by connecting a firing signal to the firing elementor elements (6, 7, 8), and a transmission device (4) for thetransmission of the firing commands (3) from the control device (2) tothe firing device (5), the firing element or elements (6, 7, 8) is/arenot fired by the firing device (5) until the last of the n+1 firingcommands (3) has been transmitted.
 5. The device as claimed in claim 4,in which the control device is a delay device (14, 20, 21, 22, 28, 29,30) for delaying the firing signal (3), the delay device (14, 20, 21,22, 28, 29, 30) being triggered by the first firing command, and havinga delay which is longer than the time which is necessary for thetransmission of all the firing commands (3).
 6. The device as claimed inclaim 4 or 5, in which the control device (2) outputs coded firingcommands (3), and the firing device (5) has a firing command decoder(12, 19, 27) for decoding the firing commands.
 7. The device as claimedin claim 4, 5 or 6, in which the firing device (5) fires a plurality offiring elements (6, 7, 8) in succession.